Printing and binding of booklets and similar materials present challenging problems. This is particularly true when a large volume of materials must be printed and bound, obviating use of manual assembly and binding techniques. The problems are compounded when different types, lengths, or contents of documents are to be printed and bound. In this situation, one must generally sort and assemble a series of pages or sheets to be bound in order to separate and bind each of the particular documents within the series.
Normally, such printing is done on offset printing devices producing stacks of sheets with each individual stack containing only one kind of sheet, i.e. stack one has multiple copies of sheet one, stack two has multiple copies of sheet two, and so on. The stacks are then placed in a gathering device with sheets pulled from each stack to create a booklet which is then bound. The result is a large number of identical booklets. This method does not lend itself to producing booklets of different length and content, particularly when they must subsequently be sequenced for use in packages requiring booklets from each of the print/binding processes. Such requirements typically cause pick and pack manual assembly.
However, one often may desire to print and bind a large number of educational test booklets, each of the booklets having possibly different information (content) and numbers of sheets. These booklets may, using computer controlled printers, be first printed on a series of sheets such that a large stack of unbound sheets contains, in appropriate final sequence, the several different test booklets. One must then determine how to separate and bind each of the particular booklets in the series. The binding is made more difficult when, for example, the test booklets each have different lengths. These problems with printing and binding are evident not just in binding test booklets, but in other materials as well.
Printing and binding of varying test booklets may involve the following steps. First, the test booklets are printed on a series of sheets. Second, the sheets are, if necessary, cut down to the appropriate size. Third, the series of sheets are separated into the individual booklets. This may be a complicated step which involves individually separating out the sheets in the series and determining which sheets correspond to each test booklet in order to determine which sheets must be bound together. Fourth, the now separated sheets are bound together.
Singulating is one technique for determining which sheets in a stack are to be bound together. In this technique, a machine receives a series or stack of pages containing the information to be bound together. The machine removes each page from the stack individually. When all sheets for a particular set are separated and grouped together in original sequence, as determined by an indexer, the machine binds together that particular set of sheets. The indexer, therefore, keeps track of which pages are to be bound together. This technique is expensive, however, and complicated when the machine jams. This requires a reprint and insertion of a corrected sheet. In addition, the indexer must be very accurate. If a failure occurs, the resulting booklet will be incorrectly bound due to fewer or greater than desired sheets being included; furthermore, the subsequent booklet by definition will also be faulty.
Using capabilities provided by many printing devices, sheets to be bound into a booklet can be indexed or offset in the stack from subsequent sets of sheets to be bound into booklets. Singulating is no longer required, but lifting unbound sets of sheets from stacks to feed into binding systems presents further complications to the binding process described above. Normal binding techniques do not operate effectively when, in sequencing, the sets to be bound can range from one sheet (i.e., no binding) to hundreds of sheets (i.e., one booklet with 1-N sheets) in uncontrolled and variable sequences.
One common technique for binding together documents is stapling. Stapling, however, also requires that each document to be bound together be removed from a stack of printed sheets. The staples sometimes cause problems. Cross motion of booklets within a stack of booklets (during printing, shipping, etc.) often results in the last page being torn from the grasp of the staple. Also, when a series of stapled documents are stacked on top of each other, the staples often catch on one another. Removing staples is expensive and difficult in the event that the booklet must be returned to individual sheets such as for machine reading and scoring of test booklets.
Another binding technique uses adhesive and tape. The adhesive is applied to the edges of the sheets to be bound together. The tape is then applied over and wrapping around the edge. With adhesive, however, the pages within a stack must still be singulated or handled as variable unbound sets, as mentioned above, in order to remove each of the individual documents to be bound together. In addition, the tape makes stacking of the booklets difficult, since the taped edges have a greater thickness than the other edges of the booklets.
Accordingly, a need exists for improved techniques for printing and binding, particularly binding of varying printed documents within a series of sheets, thereby allowing the power of intelligent, computer controlled printers to fully recognize their potential and produce booklets of various length, content, and sequence as desired.